Fuel injection pump

ABSTRACT

A fuel injection pump comprises a rotor disposed in a housing and having a pressure chamber therein, a free piston disposed slidably in the pressure chamber dividing the chamber two pump chambers, two solenoid valves for controlling fuel supply, and two preparatory chambers for metering fuel to be fed to the pump chambers. The preparatory chambers and the solenoid valves are arranged in the same plane crossing the axis of the rotor to align with each other. Fuel from a feed pump transfers to the preparatory chamber through the solenoid valve and is metered there. The metered fuel is fed to the pump chamber, pressurized there and delivered to the engine.

BACKGROUND AND SUMMARY OF THE INVENTION

This invention relates to a fuel injection pump for internal combustionengines, and more particularly to an improvement on a fuel injectionpump with preparatory chambers for metering an amount of fuel.

In a fuel injection pump, in order to improve metering precision of anamount of fuel from an electromagnetic valve for metering, and to expandinjection timing control range, it is necessary to supply metered fuelfrom the electromagnetic valve into pump chambers through meteringpreparatory chambers. Such a fuel injection pump with preparatorychambers is disclosed in prior U.S. patent application Ser. No. 467,302still pending filed by Yoshiya Takano and Yoshikazu Hoshi on Feb. 17,1983 (the corresponding European patent application Ser. No. 83101476.6filed on Feb. 16, 1983). The fuel injection pump comprises a rotordriven by the engine and a housing accomodating the rotor. In the rotor,two pump chambers are formed, and the housing is provided with thepreparatory chambers and solenoid valves for metering the fuel to be fedto the chambers. In the rotor and the housing various fuel passages andswitching valves are formed, and fuel from a fuel source is delivered tothe engine through the solenoid valves, the preparatory chambers, thepump chambers and the various fuel passages and switching valves.

In this fuel injection pump, the various passages and switching valvesare relatively complicated and more simple construction is desirable.

An object of the invention, therefore, is to provide a fuel injectionpump which is simpler in construction.

Another object of the invention is to provide a fuel injection pumpwhich is compact and stable in construction.

Briefly stated, the present invention resides in that solenoid valvesfor metering and supplying fuel and metering preparatory chambers arearranged such that fuel from said solenoid valves enters directly intosaid metering preparatory chamber.

The other features, advantageous effects, etc. of the present inventionwill be understood by description of an embodiment referring to thedrawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a sectional view of an embodiment of a fuel injuection pumpaccording to the present invention;

FIG. 2, FIG. 3, FIG. 4, FIG. 5, FIG. 6, FIG. 7, FIG. 8 and FIG. 9 aresectional views taken along a line II--II, a line III--III, a lineIV--IV, a line V--V, a line VI--VI, a line VII--VII, a line IIX--IIX anda line IX--IX of FIG. 1, respectively.

DESCRIPTION OF THE DISCLOSED EMBODIMENT

Referring now to the drawings, in FIG. 1 showing a vertical sectionalview of a fuel injection pump for a four cylinder internal combustionengine, the fuel injection pump is provided with a shaft 6, driven bythe engine and connected to a rotor 5. The rotor 5 is rotatably insertedin a sleeve 18 which is fitted to a base member 16. The sleeve 18 andthe base member 16 constitute a housing. The rotor 5 has an axial boreformed along an axis and plugs at the both ends thereby to form apressure chamber. A free piston 39 is slidably inserted in the pressurechamber and divides it into two pump chambers 24, 25. In each of thechambers 24, 25, a stopper is provided for restricting movement of thefree piston 39 within a predetermined range. At one end of the rotor 5,a feed pump 7 is provided for feeding pressurized fuel. The other end ofthe rotor 5 is connected to the shaft 6 through a coupling means. Thebase member 16 has a pair of preparatory chambers 3, 4 which aredisclosed best in FIG. 6. In FIG. 6, the preparatory chambers 3, 4 formeasuring fuel to be fed to the pump chambers are formed in a sectionalplane crossing the axis of the rotor 5 at an angle of 90° so as toextend in a perpendicular direction to a radial direction and parallelto each other. In each of the chambers 3, 4, a free piston 14, 15 isslidably disposed thereby to divide the chamber into two parts. Thepreparatory chambers 3, 4 communicate with the pump chambers 24, 25 andthe feed pump 7 through various passages and valves. Metering solenoidvalves 1, 2 for measuring an amount of fuel to be injected into thepreparatory chambers 3, 4 are mounted on the housing so that the axesalign with the preparatory chambers 3, 4 and the fuel from the solenoidvalves 1, 2 enter the chambers 3, 4 directly. The various valves andpassages formed in the rotor 5, the sleeve 18 and the base member 16 aredescribed later.

On the end portion of the rotor 5 opposite the feed pump 7, as shown inFIG. 2, an expansible chamber is disposed which comprises a compressioncam 26 secured to the housing 16, rollers 38 inserted in recesses formedin the rotor 5, shoes 37, and plungers 36. The cam 26 has fourprojections corresponding to the number of the engine cylinders whichmove the rollers, shoes and plungers inward as the rotor 5 rotates.

The shaft 6 has a timing gear 12 having pulse generators on the outerportions. A sensor 13 mounted on the housing 16 so as to face the pulsegenerator detects pulses from the timing gears 12 and transmits them tothe solenoid valves 1, 2.

In the rotor 5, the sleeve 18 and base member 16, various passages areformed, and compound switching valves are formed between the sleeve 18and the rotor 5. The feed pump 7, the solenoid valves 1, 2, thepreparatory chambers 3, 4, the pressure chamber, etc. are communicablewith each other through the various passages and the compound switchingvalves. The various passages and the compound switching valves are asfollows: (The solenoid valve 1 and the preparatory chamber 3 are in ametering fuel supply line for controlling the amount of injected fuel,and the solenoid valve 2 and the preparatory chamber 4 are in a meteringfuel supply line for controlling the timing of fuel timing controlfuel.)

8s: Fuel induction passage 8 formed axially in the sleeve 18 from thefeed pump position to VII--VII section in FIG. 7 (appears in FIGS. 7, 8,9).

9s: Peripheral groove 9 formed in the periphery of the sleeve 18 inVII--VII section and communicating with 8s (FIG. 1, FIG. 7).

10s: Induction groove 10 formed axially in the periphery of the sleeve18 from VII--VII section to VI--VI section and communicating with 9s(FIGS. 6, 7).

11h: Induction bore 11 formed in the base member 16 communicating with10s (FIG. 6).

17h: Discharge ports 17 formed in the base member 16 and communicatingwith the preparatory chambers 3 and 4, respectively (FIG. 6).

19s: Discharge ports 19 formed in the sleeve 18 and communicating with17s (FIG. 6).

20r: Discharge grooves 20 of four (4) formed in the periphery of therotor 5 equiangularly, and being communicable with 19s and 23s (laterdescribed). 20r extends axially from the VI--VI section to V--V sectionin FIG. 5, (FIGS. 6, 5).

22s: Discharge ports 22 formed in the V--V section of the sleeve 18 andbeing communicable with 20r, (FIG. 5).

23s: Supply passages 23 formed in the sleeve 18 and being communicablewith 20r and 28r (later described), (FIG. 6). 23s is communicable with11h through the solenoid valve 1, 2 disposed in the induction passage11.

27s: Supply ports 27 formed in the sleeve 18, communicating with 8s and9s and being communicable with grooves 28, (FIG. 7).

28r: Supply grooves 28 formed axially and equiangularly in the sleeve,separated from each other by 90°, extending from VII--VII section toVI--VI section, and being communicable with 19s, 23s, 27s and 29s,(FIGS. 6, 7).

29s: Supply ports 29 formed in the sleeve 18 and connected to 30s and33s, respectively, (FIG. 7).

30s: Supply groove 30 formed in the sleeve periphery, extending axiallyfrom VII--VII section to VIII--VIII section (FIGS. 7, 8).

31s: Supply hole 31 formed in the sleeve 18 and being able tocommunicate 32r with 30s, (FIG. 8).

32r: Supply holes 32 (four) formed separated from each other by 90 inthe rotor 5, communicating with the pump chamber 25, (FIG. 1, FIG. 8).

33s: Supply groove 33 formed in the sleeve 18 to extend from VII--VIIsection to III--III section, (FIGS. 1, and 3 to 7).

34s: Supply holes 34 formed in the sleeve, connected to 33s and beingcommunicable with 35r, (FIGS. 1, 3).

35r: Supply holes 35 (four) formed equiangularly, communicating with thepump chamber 24, (FIG. 3).

40r: Spill-ports 40 (four) formed in the rotor 5, communicating with thepump chamber 24, (FIGS. 1, 4).

41s: Spill-passages 41 formed in the sleeve 18, communicating with 40r,(FIG. 4).

42s: Communication passages 42 formed in the sleeve periphery, (FIGS. 3,4).

100s: Discharge groove 100 formed axially in the sleeve 18, (FIGS. 3 to5).

101r: Delivery hole 101 formed in the rotor 5, communicating with thepump chamber 25, (FIG. 7).

102s: Delivery holes (four 102, formed in the sleeve and communicablewith the delivery hole 102 (FIG. 7).

103h: Delivery ports 103 formed in the base member 16 for communicating103h with the engine through pipes (not shown) (FIG. 7).

With the above construction, fuel from the abovementioned feed pump 7 issupplied to each of the metering solenoid valve 1 for controlling anamount of fuel to be injected into the engine and the metering solenoidvalve 2 for controlling injection timing through passages of8s-9s-10s-11h. In the state shown in FIG. 1, electric pulses are givento the valves 1, 2 to open them, an amount of fuel corresponding to theelectric pulses for opening is supplied directly into the preparatorymetering chambers 3, 4 at timing corresponding to the electric pulse.The timing at which the valve opening pulses are applied to the valves1, 2 is determined by detecting signals from the timing gear 12 with thesensor 13. In the preparatory valves 3 and 4 receiving fuel, the freepistons 14 and 15 are moved left in FIG. 6, and the fuel contained inthe chambers on the left of the free pistons 3, 4 is discharged into alower pressure portion (not shown) of the fuel injection pump throughthe passages 17h→19s→20r→22s→100s, whereby the metering operation ofmeasured fuel to the preparatory chambers 3, 4 on the right side of thefree pistons 14, 15 is completed.

In addition to this metering operation, the fuel already contained inthe pump chambers 24 and 25 is pressurized by the operation of thecompression cam 26. In this stage, the metering and temporaryaccomodation of fuel by the solenoid valves 1, 2 and the preparatorychambers 3, 4 are effected while the compression of fuel in the pumpchambers 24, 25 is carried out for injection thereof into the engine.

In order to supply the metered fuel contained in the preparatorychambers 3, 4 into the pump chambers 24, 25, the rotor 5 is rotated by45°. At this time, the rotor 5 is shifted angularly by 45° relatively tothe sleeve 18 from the position of FIGS. 1 to 9. In this relativeposition between the rotor 5 and the sleeve 18, pressure raised by thefeed pump 7 as a pressure source reaches the preparatory chambers 3, 4on the left side of the free pistons 14, 15 through the passages8s--27s--28r--19s--17r, thereby to move the free piston to the rightside. By this operation, the metered fuel contained in the preparatorychamber 3 on the right side of the free piston 14 is fed to the pumpchamber 25 through the passages 23s--28r--29s--30s--31s--32r, (FIGS. 6,7, 8). Further, the metered fuel contained in the preparatory chamber 4on the right side is fed to the pump chamber 24 through the passages23s--28r--29 s--33s--34s--35r (FIGS. 6, 7, 3). As the fuel is fed to thepump chamber 4, the plungers 36, the rollers shoes 37 and the roller 38are moved outward so that the chamber 24 is expanded by the volumecorresponding to the amount of the fuel fed to the chamber 4, wherebythe operation of supply of the metered fuel contained in the preparatorychamber 4 is carried out.

After completion of the above-mentioned fuel supply to the pump chambers24, 25, further, the rotor 5 is rotated by 45° so that the relativeposition between the rotor 5 and sleeve 18 is returned to the positionshown in FIGS. 1 to 9. In the FIGS. 1 to 9, the metering state and thecompression period state are shown.

In the same manner as above, every time the rotor 5 rotates by 45°, theabove metering and compression operation and the fuel supplyingoperation are carried out alternately.

The compression is carried out in the following manner as shown in FIGS.1 and 2, when fuel is fed to the pump chamber 24. Namely, as the rotor 5rotates, the rollers 38 contact projections of the cam 26, whereby therollers 38, the roller shoes 37 and the plungers 36 are pressed inwardlyso that the fuel in the pump chamber 24 is highly pressurized. The timethe fuel is pressurized is determined by the contact position betweenthe cam 26 and the roller 38. The contact position, that is, fuelinjection timing can be controlled by an amount of the fuel fed to thepump chamber 24. The amount of the fuel can be controlled by an amountof fuel sent from the solenoid valve 2, that is, valve opening pulsewidth applied to the solenoid valve 2.

As above-mentioned, when the fuel in the pump chamber 24 is made high inpressure, the free piston 39 is moved to the right side, and theinterior of the pump chamber 25 is pressurized in turn. Therefore, thefuel in the pump chamber 25 is delivered into the combustion chamber ofthe engine through the passages 101r--102s--103h-- a delivery valve (notshown)-- a pressure pipe (not shown)-- an injection valve (not shown).

As the fuel is injected on, the left end of the free piston 39 is movedin the pump chamber 24 thereby to start to open the spill-port 40 whichhas been closed by the free piston 39.

Therefore, the fuel in the pump chamber 24 begins to be dischargedthrough the passages 40r--41s--42s. Consequently, pressure in the pumpchamber 24, in turn, pressure in the pump chamber 25 drops thereby tobring the injection of fuel into the engine to an end, and the pumpchamber 24 starts to shrink by contact between the rollers 38 and theprojections of the cam 26, whereby the fuel discharge from the pumpchamber 24 is ended. Further, in the pump chamber 25, all the amount offuel fed thereto from the solenoid valve 1 through the preparatorychamber 3 is fed to the engine. Therefore, the amount of fuel to beinjected can be controlled precisely by opening the solenoid valve 1according to the opening pulse width applied thereto.

As apparent from the above-mentioned, in the present invention, fuelpassages from the solenoid valves 1, 2 to the preparatory chambers 3, 4do not rely on passages of the compound switching valve, and thepreparatory chambers 3, 4 communicate directly with the immediatelydownstream portions of the solenoid valves so that the fuel injectionpump can be made simpler as compared with the other construction of offuel injection pump with preparatory chambers. Further, the solenoidvalves 1, 2 can be arranged coaxially of the preparatory chamber so thatthe fuel injection pump can be made more compact and stable.

What is claimed is:
 1. A fuel injection pump for an internal combustionengine comprising:a rotor disposed in a housing and being rotatableaccording to rotation of the engine; a pressure chamber formed in saidrotor; a first free piston slidably inserted in said pressure chamber,and dividing said pressure chamber into a first pump chamber and asecond pump chamber, said first pump chamber being communicable with theinterior of the engine through delivery passages and said second pumpchamber being communicable with discharge passages for discharging thefuel therein; means for pressurizing fuel in said pressure chamberaccording to the rotation of said rotor thereby delivering fuel to theengine; a pair of preparatory chambers for metering and supplying fuelinto said pressure chamber, each of said preparatory chambers beingprovided with a second free piston which divides its preparatory chamberinto first and second preparatory chambers; and a pair ofelectromagnetic valves for controlling feeding of fuel to respectiveones said first preparatory chambers, wherein said electromagneticvalves are arranged to communicate directly with respective ones of saidfirst preparatory chambers for supplying fuel thereto withoutintervening valves.
 2. The fuel injection pump of claim 1, wherein saidpair of electromagnetic valves and said pair of preparatory chambers arearranged such that their axes are disposed in substantially the sameplane crossing the axis of said rotor.
 3. The fuel injection pump ofclaim 2, wherein said plane crosses the axis of said rotor at a rightangle.
 4. The fuel injection pump of claim 3, wherein saidelectromagnetic valves are aligned with respective ones of said pair ofpreparatory chambers.
 5. A fuel injection pump for internal combustionengines comprising:a rotor disposed in a housing and being rotatableaccording to rotation of the engine; a pressure chamber formed in saidrotor; a first free piston slidably inserted in said pressure chamber,and dividing said pressure chamber into a first pump chamber and asecond pump chamber, said first pump chamber being communicable with theinterior of the engine through delivery passages, and said second pumpchamber being communicable with discharge passages for discharging thefuel therein; means for pressurizing fuel in said pressure chamberaccording to the rotation of said rotor thereby delivering the fuel tothe engine; a pair of preparatory chambers for metering amounts of fuelto be supplied to said pressure chamber, each of said preparatorychambers provided with a second free piston which divides itspreparatory chamber into first and second preparatory chambers; a pairof electromagnetic valves for controlling feeding of fuel to respectiveones of said first preparatory chambers, said electromagnetic valvesbeing arranged to communicate directly with said first preparatorychambers so that supply of fuel from said electromagnetic valves to saidfirst preparatory chambers is controlled only by said electromagneticvalves; first fuel passage means for leading fuel from a feed pump tosaid first preparatory chambers by way of said electromagnetic valveswhich control the feeding of fuel to said first preparatory chambers;second fuel passage means for leading fuel from said first preparatorychambers to said pressure chamber; third fuel passage means for leadingfuel from said feed pump to said second preparatory chambers; fourthfuel passage means for discharging fuel out of said second preparatorychambers; and fuel passage switching valve means provided on saidsecond, third and fourth fuel passage means for switching the same fuelpassage means according to rotation of said rotor.